The aftermarket gears were a pretty ugly solution to the problem in any case: they consisted of a stack of steel stampings riveted together, and their teeth were triangular, not involute form. This means they damaged the small aluminium pinions they had to mesh with.
Cutting gears requires a milling machine, a dividing head or rotary table, and the specific involute-form gear cutter to match that gear. While most serious machine shops have the milling machine and dividing head, not so many have a full range of involute cutters. Cutting a gear with the wrong cutter gives a result about as bad as those steel gears with the triangular teeth, but at the same high cost as cutting a perfect gear. Accurate gear cutting also requires making some calculations about center distance corrections, and setting the milling machine up very accurately. Doing this without having the original drawing of the part, can be quite time-consuming. Essentially, it is a job for a trade-qualified machinist, not a fitter and turner or other tradesman. Having said that, keen amateurs make gears for antique machinery all the time, sometimes with moderate success - but it will take a number of hours, it may take more than one try, and usually it won't be an accurate, well-cut gear. Incidentally, once the equipment is correctly set up to make one gear, it can make a dozen more quite quickly.
